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 Solder strength...
AEnemaBay  [Team Member]
11/9/2011 11:39:09 PM
Does anyone have a general idea how much radial torque a low temp soldered piece of metal can take? I have a breeching washer that I need to add to a FAL barrel and I want to permanently attach it to the barrel and match the contours and flats (so it doesn't look like a breeching washer was used).

Would low temp (281 F) solder be able to take a radial torque around 125-150 ft./lbs.?
dfariswheel  [Member]
11/11/2011 5:17:24 PM
Since no one else has responded:

I'm not sure about whether low temp solder would hold.
Instead of the low temp, I'd go with the slightly higher temp soft solder that contains about 3% silver.
The silver prevents the solder from tarnishing and adds strength. That will hold better, but I'm still not sure whether it'll hold for what you're doing.

This is NOT "silver solder" which is really silver braze and melts at temps above 1100 degrees. This is a true soft solder. It melts about 400 to 450 degrees which is low enough not to cause any problems. As with all soft solders, don't over heat the metal. 450 degrees is not that hot. Too many people heat the metal until it starts to change color, which is WAY too hot.
The problem is they fail to get the metal really clean and the solder won't flow, so they heat it hotter and hotter trying to get it to go.

You can buy this 3% silver bearing soft solder at Walmart and most hardware stores. Use a good flux and have a tight fit on the parts. The tighter the fit, the better solders hold.
AeroE  [Moderator]
11/12/2011 9:47:32 AM
I have some allowables for different types of solders at work.

On terminology:

Radial would be loads running from the center of the cylinder to the outer diameter, or the reverse of that. What you're doing is applying circumferential loads via friction between the mating surfaces. The magnitude of the friction is determined by the torque applied and the coefficient of friction between the parts, which itself is determined by the materials being mated and any lubrication in the joint.


What I would do is solder the washer with plain ol' low temp solder, the 2% silver stuff from the hardware store is a good choice. Clean the surfaces first. Then give it a try. If the joint breaks, it's no big deal to take everything apart, clean it up, and you're not out much time or money. I'll bet it works fine.

AEnemaBay  [Team Member]
11/12/2011 9:57:21 AM
Originally Posted By AeroE:
I have some allowables for different types of solders at work.

On terminology:

Radial would be loads running from the center of the cylinder to the outer diameter, or the reverse of that. What you're doing is applying circumferential loads via friction between the mating surfaces. The magnitude of the friction is determined by the torque applied and the coefficient of friction between the parts, which itself is determined by the materials being mated and any lubrication in the joint.


What I would do is solder the washer with plain ol' low temp solder, the 2% silver stuff from the hardware store is a good choice. Clean the surfaces first. Then give it a try. If the joint breaks, it's no big deal to take everything apart, clean it up, and you're not out much time or money. I'll bet it works fine.



Thanks AeroE and dfariswheel. Circumferential was the word I meant to use but it didn't sound right to me when I was typing it out. I'll just go ahead and pick up some regular low temp solder and see what happens.
AEnemaBay  [Team Member]
11/13/2011 3:54:06 PM
Well, you were right. The regular off the shelf solder (455 degree solder paste) worked just fine.
relentlessknives  [Member]
11/14/2011 7:17:37 PM


This stuff is real strong....you can get Grainger to order it for you.

It's made by Harris....BRGT31